Fair Value Measurements - Additional Information Relating To Asset-Backed Securities and Collateralized Debt Obligations (Detail) - Level 3 $ in Millions	Mar. 31, 2024 USD ($)
Asset-backed securities available-for-sale
Fair Value Of Other Financial Instrument [Line Items]
Trading asset-backed securities and related collateral	$ 102
Other \| BBB - B
Fair Value Of Other Financial Instrument [Line Items]
Trading asset-backed securities and related collateral	91
Alt A \| Home equity \| AAA - A
Fair Value Of Other Financial Instrument [Line Items]
Trading asset-backed securities and related collateral	$ 11

The fair value as of the balance sheet date of firm holdings in mortgages, mortgage backed securities (investment instruments that represent ownership of an undivided interest in a group of mortgages, where principal and interest from the individual mortgages are used to pay investors' principal and interest on the mortgage backed security) and asset-backed securities that are primarily paid from the cash flows of a discrete pool of receivables or other financial assets (such as credit-card receivables), either fixed or revolving, that by their terms convert into cash within a finite time period. Includes both pledged (to counterparties as collateral for financing transactions) and unpledged holdings.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Name Accounting Standards Codification
-Topic 940
-SubTopic 320
-Section 45
-Paragraph 2
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481961/940-320-45-2

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant